The present invention relates to Computer Numerically Controlled (CNC) Systems for material processing, and more particularly to an assembly that provides for movement of a workpiece operated on by a CNC System.
CNC systems may be used for, among other things, cutting, drilling, milling, and machining of workpieces with automated production. CNC movement is controlled by parts or cutting files generated by Computer Aided Design (CAD) software and Computer Aided Manufacturing (CAM) technology. The cutting file directs the machine through a series of steps. The instructions direct the system with respect to where the workpiece is to be cut and in what order the cuts are to be made. The cuts may be straight line or circular. Once the CNC program is written and stored in the controller, manual action is normally limited to setting up the part, starting the CNC controller that executes the program, and carrying out any necessary manual operations such as tool changes.
CNC tools may generally be “three-axis,” “four-axis,” or “five-axis” machines. A three-axis machine is one that allows the tool to move linearly along mutually orthogonal x-, y-, and z-axes of a fixed coordinate system. The x-axis may be considered to be horizontal and to extend along the longitudinal axis of the system; the y-axis is also horizontal, perpendicular to the x-axis, and across the longitudinal axis of the system; and the z-axis is vertical. A four-axis machine is one that allows the tool to move linearly along mutually orthogonal x-, y-, and z-axes of a fixed coordinate system and also allows rotation of a workpiece about a rotary axis. A five-axis machine usually puts a “wrist-like” fourth and fifth axis on the z arm of a three-axis machine to allow full tangential motion of a cutter in relation to the work surface. Numerical control allows digital accuracy to position the axes of a machine and to control other factors such as the cutting speeds and feeds for a machining pattern. This positioning and control information (the Numerical Control (NC) data) makes up an NC part program or “cutting file” that is created by a programmer. It can be used repeatedly to make multiple parts. After they are created, the cutting files are stored in a memory of the control system of the CNC tool. The CNC tool reads the cutting file in order to machine a part.
Traditional CNC systems include a base, defined by horizontal rails and intermediate members, that supports a horizontal table on which a workpiece is disposed. An intermediate piece that may be cut into by the tool when the tool passes through the workpiece may be used to protect the table rather than cutting into the table. The base and the components it supports are fixed, and it is the tool that moves about all applicable axes. The size of the workpiece is limited by the size of the base, so if large workpieces are desired to be processed, a correspondingly large base is required. In addition, the base size determines the footprint of the system, so the larger the base, the larger the footprint of the system, and the area housing the system has to accommodate that footprint.
Other CNC systems have a reduced footprint and may have a table that moves along the x-axis instead of the tool moving along that axis. Such movement can reduce the length of the base, and accordingly can reduce the footprint of the system. The bases of such systems, however, generally do not extend far enough to provide for processing of materials with significant length, so they are limited to handling relatively short workpieces.